lgrkPower {factorial2x2} | R Documentation |
Computes the power for the unstratified (ordinary) logrank statistic for two group comparison.
lgrkPower(hr, nevent, alpha = 0.05, rprob = 0.5)
hr |
hazard ratio |
nevent |
expected number of events |
alpha |
two-sided significance level |
rprob |
randomization probability |
Uses the formula at the bottom of p.317 from Schoenfeld (Biometrika, 1981) where the beta should be 1 - beta. The formula is modified to assume that values of the hazard ratio less than 1 correspond to treatment efficacy. We do this because we only want to include the probability of rejecting the null in favor of efficacy, not inferiority as well.
power |
logrank power |
Eric Leifer, James Troendle
Schoenfeld, D. The asymptotic properties of nonparametric tests for comparing survival distributions. Biometrika. 1981; 68: 316-319.
hr <- 0.5 nevent <- 98 lgrkPower(hr, nevent, alpha = 0.05, rprob = 0.5) # $power # [1] 0.9293463